After her aunt is murdered by the Master, an airline stewardess named
Tegan Jovanka becomes an unwitting stowaway aboard the TARDIS as it
travels to the planet Logopolis. There, the Doctor discovers that the
Master's interference with the Logopolitans' advanced mathematics has
unleashed a wave of entropy which threatens to consume the entire
universe. The two Time Lords enter into an uneasy alliance, together
with Adric, Tegan and Nyssa, who has travelled to Logopolis to confront
the Master. Their only hope lies on Earth... but then, in the moment of
greatest crisis, the Master plays his ultimate trump card.

Production

On November 2nd, 1979, shortly after John Nathan-Turner had been
appointed as the new producer of Doctor Who, he and executive
producer Barry Letts were approached by Head of Drama Graeme McDonald
about a new funding initiative for the series. Doctor Who had
been a popular element of the Australian Broadcasting Commission's
line-up for many years, and McDonald suggested the possibility of
entering into a coproduction arrangement with the ABC. Always mindful of
finding ways to boost his show's meagre budget, Nathan-Turner agreed and
entered into negotiations with the ABC that lasted well into 1980; their
discussions centred on filming one or two serials in Australia during
the making of Season Nineteen. By the end of July, however, no deal had
been reached and it became apparent that this proposal would have to be
shelved for the time being.

Nathan-Turner was not inclined to give up on the initiative yet,
however, and began casting about for ways to make Doctor Who more
attractive to the ABC. At this point, he and script editor Christopher H
Bidmead were developing a new female character to replace Romana, who
would be written out of the show late in Season Eighteen. (An earlier
plan to bring back a popular former companion had had to be abandoned
when both Elisabeth Sladen, who had played Sarah Jane Smith, and Leela
actress Louise Jameson had declined Nathan-Turner's invitation to return
to Doctor Who.) Nathan-Turner now suggested that the new
companion should be Australian, with the hope that the inclusion of an
Antipodean regular would make the ABC's potential investment in
Doctor Who more palatable.

John Nathan-Turner envisioned the new companion as someone
whose forthrightness would mask her lack of self-confidence

Nathan-Turner and Bidmead envisioned the new companion as a bolshy air
hostess who would be willing to stand up to the Doctor, but whose
forthrightness would privately mask her lack of self-confidence.
Nathan-Turner suggested two names for the character: Tegan (actually a
Celtic name which Nathan-Turner selected as an homage to the niece of an
Australian friend) and Jovanka (inspired by Jovanka Broz, the wife of
Yugoslav President Josip Broz Tito). Bidmead inadvertently interpreted
“Tegan Jovanka” as the new companion's full name, and the
error stuck. A character outline for Tegan Jovanka was issued on August
1st. Unfortunately, by the end of August the ABC had confirmed that they
still were not interested in a Doctor Who coproduction deal.

It was planned that Tegan would be introduced in the final story of
Season Eighteen -- which would also be Tom Baker's last Doctor
Who adventure after seven years. Nathan-Turner and Bidmead had
decided to bridge the transition from Baker to his successor with a
trilogy of stories resurrecting the Doctor's Time Lord archnemesis, the
Master. This would begin with The Keeper Of
Traken, the year's penultimate adventure, and conclude at the
start of Season Nineteen. Bidmead had had enormous problems bringing
suitable new writers onto Doctor Who, however, and had found the
job of script very trying. By August, he had decided to leave the
programme, but reluctantly agreed to provide the season finale himself;
staff clearance was secured on August 29th.

In addition to introducing Tegan, regenerating the Doctor, and
spotlighting the Master, Bidmead decided to use Serial 5V to tie up
loose threads from earlier in the year. The three middle stories of
Season Eighteen had all dealt with the Doctor's adventures in the pocket
universe of E-Space, accessed after the TARDIS is drawn into a Charged
Vacuum Emboitment (CVE). Bidmead decided to further explore the notion
of the CVEs in what came to be called Logopolis (taken from the
Greek for “city of words”).

Bidmead was also a keen computer enthusiast, and used many ideas from
computer science in developing his scripts, with elements such as the
Monitor, block transfers, and registers all being derived from
terminology in computer architecture. Eager to inject Doctor Who
with real scientific notions, Bidmead also drew upon the physics
discipline of thermodynamics, making heavy use of the concept of
entropy: the measure of unavailable energy in a system, which
effectively increases as a system becomes homogeneous. Another starting
point was Nathan-Turner's observation that a real police box still stood
on the Barnet bypass in London. Bidmead was fascinated with the TARDIS,
and wanted to explore its properties more fully.

A computer enthusiast, Christopher Bidmead used many ideas
from computer science in developing his scripts

As Bidmead worked on Logopolis, Nathan-Turner informed him that
he was considering retaining the character of Nyssa, whom writer Johnny
Byrne had introduced in The Keeper Of
Traken, as a third companion alongside Tegan and Adric. Bidmead
duly inserted Nyssa into his plans for Logopolis. The mystery
surrounding the Watcher was felt to be a crucial element to hold the
viewers' interest, and so it was decided to hold off the Master's first
onscreen appearance until episode three, in order to make the audience
wonder if the Watcher might actually be the evil Time Lord.

Meanwhile, Nathan-Turner had begun to consider actors for the role of
the Fifth Doctor. He was uncertain about what direction to take, but was
well aware that Baker would cast a long shadow after appearing in
Doctor Who for so many years, and hence the new Doctor would have
to be as different from Baker's incarnation as possible. Nathan-Turner
approached character actor Richard Griffiths (perhaps best known at that
time for his humorous Shakespearean roles and the 1975 film It
Shouldn't Happen To A Vet), but Griffiths was unavailable. He also
considered Scots actor Iain Cuthbertson, who had memorably appeared in
programmes such as Budgie, The Stone Tape and
Sutherland's Law, and who had played Garron in the 1978 Doctor
Who story The Ribos Operation.

Nathan-Turner's office wall was covered with photographs from the
various productions on which he had worked. One of his most significant
assignments prior to becoming Doctor Who's producer had been as
production unit manager on the veterinary drama All Creatures Great
And Small, which had already influenced a number of his choices for
Doctor Who writers and directors. Now one of these photos -- of a
charity cricket match which included All Creatures Great And
Small star Peter Davison -- caught Nathan-Turner's eye. The producer
realised that the younger and fair-haired Davison was a striking visual
contrast to Baker, and also knew that All Creatures Great And
Small had earned Davison a fan following which might pursue him to
Doctor Who. During October, Nathan-Turner contacted Davison and
offered him the role of the Fifth Doctor.

Peter Davison's reaction was to turn down the role of the
Fifth Doctor, but he could not bear to see someone else win the part

Davison's initial reaction was to turn down the part. He was wary of
getting involved in a show like Doctor Who which had virtually
become a British institution, and also feared that, at 29 years old, he
was simply too young to play the Doctor. Nathan-Turner was not so easily
deterred, however, and gave Davison more time to consider the offer.
After a couple of weeks, Davison came to the realisation that he simply
could not bear to see someone else win the role, and informed the
producer of his change of heart.

This marked the latest plateau for Davison in a remarkable rise through
the ranks of Britain's entertainment industry. After enduring a variety
of jobs -- including mortuary attendant -- Davison had begun working at
the Nottingham Playhouse. He had then moved into television, quickly
securing a recurring role in the science-fiction series The Tomorrow
People (where he met his future wife, Sandra Dickinson). Davison was
then a regular on Love For Lydia before winning the role of
Tristan Farnon on All Creatures Great And Small. More recently,
Davison had earned starring roles in the sitcoms Holding The
Fort and Sink Or Swim, and was due to record a cameo
appearance in the TV version of The Hitchhiker's Guide To The
Galaxy. Davison's real surname was Moffett; he had adopted his stage
name to avoid confusion with director Peter Moffatt (who had directed State Of Decay for Doctor Who's
eighteenth season).

At the same time, Nathan-Turner had to find an actress to play Tegan. He
was eager to cast an Australian, and more than one hundred thespians
were interviewed during the autumn. One of the last performers who
auditioned was Janet Fielding; she had been recommended to Nathan-Turner
by a friend at the Actors' Alliance who reckoned that Fielding was a
perfect fit to play “a bossy Australian”. Born Janet Mahoney
in Brisbane, Australia, Fielding had originally planned to be a
journalist, but decided instead to become an actress. Travelling to
England in the late Seventies, she had worked in theatre with people
like Ken Campbell before securing a small role in Hammer House Of
Horror.

At her audition, there was some concern that Fielding was too short to
play an air hostess like Tegan, but Fielding convinced Nathan-Turner
that the minimum height requirement for stewardesses in Australia was
less than in Britain due to the smaller stature of people from that part
of the world. This was Fielding's second fib -- she had also claimed to
be three years younger than her true age -- but it paid off: on October
23rd, she was was contracted for three serials beginning with
Logopolis, with an option for twelve further episodes. A
photocall to introduce the new companion was held the same day.

Tom Baker and John Nathan-Turner colluded to stir up
publicity by suggesting that the Fifth Doctor might be a woman

On October 24th, even more press attention was called to Doctor
Who when word leaked out of Baker's imminent departure.
Nathan-Turner hastily arranged a press conference, and he and Baker
colluded to stir up further publicity with Baker hinting that the Fifth
Doctor might be played by a woman. The truth was revealed on November
5th, when Davison appeared on Nationwide to confirm that he would
be replacing Baker. On the 11th, he was contracted for twenty-eight
episodes: at this stage, Season Nineteen was still intended to be the
same length as Season Eighteen.

Fielding's first Doctor Who work also marked the beginning of
location recording for Logopolis. The director was Peter
Grimwade, who had recently completed Full
Circle. On December 16th, filming began with the material at
Aunt Vanessa's residence. When the crew was unable to locate the owner
of the house that Grimwade had originally intended to use, they instead
moved further up the same street to the home of Andrew McCulloch, who
had cowritten Meglos earlier that year.
Next, all of the scenes beside the River Thames were completed, with
recording taking place on the Albert Bridge and the Cadogan Pier at the
Chelsea Embankment. Tom Baker rejoined the Doctor Who team just
three days after his wedding to former costar Lalla Ward, who had played
Romana.

Filming was originally planned to continue on the 17th, but an
industrial dispute delayed one day of studio work on The Keeper Of Traken to this date. Instead,
production on Logopolis resumed on the 18th, when the BBC
Overseas Monitoring and Receiving Station at Crowsley Park in Sonning
Common, Berkshire, posed as the grounds of Pharos Project. This left
only the material involving the genuine police box to be filmed.
Unfortunately, the police box located near the Barnet bypass had fallen
into disrepair and had recently been dismantled. As luck would have it,
however, the TARDIS prop used until the end of Season Seventeen had been
placed in storage. This was now summoned back for use in these
sequences, which were recorded on December 19th and 22nd at a lay-by
between Denham and Amersham in Buckinghamshire.

Production then paused for the Christmas holidays. At this point,
Bidmead concluded his appointment as Doctor Who's script editor,
leaving interim script editor Antony Root to carry on solo. Bidmead
retained his ties to the programme, however, contributing scripts for Castrovalva and Frontios during the next three years. Two
further submissions -- “In The Hollows Of Time” and
“Pinocotheca” -- were abandoned during the mid-Eighties.
Bidmead novelised all three of his televised Doctor Who stories
for Target Books. He also wrote a script entitled Renaissance Of The
Daleks for Big Finish Production's range of Doctor Who audio
adventures, although disagreements with Big Finish led to Bidmead
leaving the project before its 2007 release. Bidmead otherwise
concentrated on his career as a computer journalist, writing for various
computer-related publications. Around the start of 1994, Bidmead became
one of the first Doctor Who professionals to interact with fandom
via the still-nascent Internet.

Tom Baker was unhappy with the Doctor's final scenes,
feeling that they looked unheroic

Logopolis resumed production with a two-day studio block in BBC
Television Centre Studio 3. January 8th dealt with all of the scenes
inside the TARDIS, while the 9th was concerned with the action in the
antenna control room and atop the gantry itself. Baker had an angry
disagreement with Nathan-Turner and Grimwade, who wanted him to yell as
the Doctor falls from the scaffolding. Baker felt that this would be
unheroic, and refused. The regeneration was also taped on this day, and
represented Davison's first work on Doctor Who. Baker was again
unhappy, and took issue with the fact that the final image that viewers
would see of his Doctor would be of him lying prone, being photographed
from above.

The season's last studio session was a three-day affair spanning January
22nd to 24th, and took place in TC6. The first day dealt with the scenes
in and around the Pharos Project computer room, as well as those in the
streets of Logopolis and at the landing area. January 23rd concentrated
on sequences in the External Register and the Control Register. Finally,
on the 24th, all the material depicting the ruined Logopolis was
completed.

Tom Baker returned to play the enigmatic Curator in the
50th-anniversary special The Day Of The
Doctor

Logopolis was the last Doctor Who story to credit Barry
Letts as the programme's executive producer (although he also did some
work on Four To Doomsday, the first serial
of the show's nineteenth recording block). It was now felt that
Nathan-Turner had enough experience to guide Doctor Who without
Letts' supervision, and so the position of executive producer was
abandoned. As Letts' name faded from view at the end of Logopolis
part four on March 21st, Doctor Who's tumultuous eighteenth
season drew to a close.

Tom Baker's career experienced something of a lull immediately following
his departure from Doctor Who, and his marriage to Ward ended in
divorce in April 1982. Letts provided Baker with his first
post-Doctor Who role, as Sherlock Holmes in The Hound Of The
Baskervilles. Baker soon found himself once again in demand, racking
up appearances on stage, on the silver screen and on television,
including Blackadder, The Chronicles Of Narnia: The Silver
Chair, Medics, the revival of Randall & Hopkirk
(Deceased), and Monarch Of The Glen. His considerable voice
work included a regular role as the narrator for Little Britain.
Baker returned to play the Fourth Doctor in the thirtieth-anniversary
Doctor Who charity special Dimensions In
Time in 1993, and the enigmatic Curator in 2013's
fiftieth-anniversary celebration The Day Of The
Doctor. He also provided linking narration for the VHS release
of the incomplete Shada, and recorded a
retrospective of his time on Doctor Who, released by BBC Video as
Doctor Who: The Tom Baker Years. More recently, Baker has
returned to play the Fourth Doctor on audio for both AudioGO and Big
Finish Productions.